The striatum is a subcortical structure that is heavily interconnected with the neocortex and that is thought to function in relation to sensorimotor learning, motivation action planning, and habit formation. Neural processing in the striatum is also thought to influence cognitive functions of the frontal lobes, because the main cortically-directed outputs of the striatum lead to the frontal cortex. Prior anatomical work has shown that the striatum has a modular anatomical architecture. The hypothesis to be tested is that the striatum also has a modular functional architecture that can be detected with state-of-the-art ensemble recording methods. The goals of the proposed work are (1) to use tetrode technology to record ensemble activity from the striatum of rats as they perform behavioral tasks designed to engage striatal networks; and (2) to analyze the population neuronal activity recorded to determine whether striatal networks show spatiotemporal patterns of activity and whether these change dynamically as the animals learn. It is hypothesized that patterns of coherent task-related activation will appear across groups of neurons recorded by single tetrodes within a ca. 100 um diameter and groups of neurons recorded by multiple tetrodes separated by 400-500 um. This range of recording space should allow monitoring of neural activity in single anatomical modules (ca. 200-300 um) and across adjoining anatomical modules. It is further hypothesized that task-related activity patterns will change with learning and that additional patterns may appear as animals learn striatum-based tasks. The ultimate objective of this work on the spatiotemporal dynamics of neuronal activity in the striatum is to understand the role of striatal activity in cortico-basal ganglia loop function. This research has potential significance for understanding network activity of complex circuits in a major subcortical structure. This research also has potential significance for clinical work in that it should provide basic science insights into the neural basis of motor and cognitive functions that are disabled in cortico-basal ganglia disorders.